EXCLUSIVE – Two weeks after Russia fired on and seized three Ukrainian vessels in the contested Kerch Strait, satellite images obtained exclusively by Fox News on Sunday show that additional forces may be headed to the region.

In the images taken on Saturday, three Russian Ilyushin -76 cargo planes were spotted in the Dzhankoi airbase in Crimea.

The Ilushin-76 cargo planes are used by the Russian army to deliver outsized or heavy cargo. (ImageSat International)

The images, captured by Imagesat International, appear to show that Russia is continuing to step up and consolidate its military forces in the Crimea, which it annexed from Ukraine in 2014.

According to social media reports in Russia, Four IL-76 planes departed on December 6 from Anapa airport in Novorossiysk and landed in Dzhankoi.

One of those airplanes returned Saturday to Anapa, while the three remain on base.

Ilushin-76 cargo planes are used by the Russian Army to deliver outsized or heavy cargo unable to be carried on the ground. The cargo planes are also used for mobilizing large numbers of troops.

RUSSIA DEPLOYS S-400 SURFACE-TO-AIR MISSILE BATTERY IN CRIMEA, SEEN IN NEW SATELLITE IMAGES

The base of the elite unit of the Russia Airborne troops, the 7th Guards Mountain Air Assault Division is located in Novorossiysk, not far from Anapa.

The division's troop participated in the last round of violence between Ukraine and Russia in August 2014, in addition to the fighting in Syria.

The three Russian Ilyushin -76 cargo planes were spotted at the Dzhankoi airbase in Crimea. (ImageSat International)

The IL-76 were spotted in the same airbase where the fourth S-400 surface-to-air missile battery was deployed, Fox News has previously reported.

The mobile S-400 missile has a range of up to almost 250 miles and can climb to an altitude of almost 19 miles. It's intended to bring down a variety of aerial threats, from aircraft to cruise and ballistic missiles.

The apparent troop buildup comes as Ukraine's defense ministry warned Friday that it will soon send naval ships through the Kerch Strait.

Ukraine demands release of sailors in Russian custody

Ukraine considering martial law after Russia seizes naval vessels; Trey Yingst reports on how both governments are responding to the conflict.

Ukraine has responded to the actions by Russia by introducing martial law for 30 days, a measure Kiev did not take even after Crimea's annexation and amid large-scale fighting between Ukrainian forces and Russia-backed separatists in 2014-2015.

As part of martial law, Ukraine has beefed up its forces on the border with Russia and called up reservists for training. Ukrainian Defense Minister Stepan Poltorak told reporters on Friday that his country intends to send naval ships through the Kerch Strait soon, saying that "otherwise Russia will fully occupy the Sea of Azov."

The intelligence report by ImageSat International indicates that the infrastructure for the S-400 battery was prepared in recent months, a long time before last weekend's naval encounters that sparked new tension between Russia and Ukraine.

The images showed a bare ground in April 2018, and construction by November 10 – two weeks before the recent escalation.

The infrastructure for the S-400 battery was prepared in recent months, a long time before the incident that sparked the new tension between Russia and Ukraine. (ImageSat International)

The image captured Sunday confirms the deployment. The eight launchers of the S-400 battery are divided into four, which are located in the southwest area of the airbase — as well as two radar systems and several trucks nearby. One of them is suspected to carry S-400 missiles.

The mobile S-400 missile has a range of up to almost 250 miles and can climb to an altitude of almost 19 miles. It's intended to bring down a variety of aerial threats, from aircraft to cruise and ballistic missiles.

The images show a bare ground followed by construction – before the recent escalation between Russia and Ukraine. (ImageSat International)

On November 28, 2018, the Russian defense ministry issued a statement, days after Russian warships seized multiple Ukrainian naval vessels, escalating the conflict with Ukraine over the land Russia annexed in 2014.

Russia has bolstered the Black Sea peninsula’s military defenses with three S-400 systems since 2017. The present deployment reinforces already existing S-400 batteries.

KIEV, Ukraine – Ukrainian officials on Friday upped the ante in the growing confrontation with Russia, announcing a travel ban for most Russian males and searching the home of an influential cleric of the Russian Orthodox Church.

The long-simmering conflict bubbled over Sunday when Russian border guards rammed into and opened fired on three Ukrainian vessels near the Crimean Peninsula, which Moscow annexed in 2014. The vessels were trying to pass through the Kerch Strait on their way to the Sea of Azov. The Russians then captured the ships and 24 crew members.

The Ukrainian parliament on Monday adopted the president's motion to impose martial law in the country for 30 days in the wake of the standoff.

There has been growing hostility between Ukraine and Russia since Moscow's annexation of the Crimean Peninsula from Ukraine in 2014. Russia has also supported separatists in Ukraine's east with clandestine dispatches of troops and weapons. Fighting there has killed at least 10,000 people since 2014 but eased somewhat after a 2015 truce.

Petro Tsygykal, chief of the Ukrainian Border Guard Service, announced at a security meeting on Friday that all Russian males between 16 and 60 will be barred from traveling to the country while martial law is in place.

Video

President Petro Poroshenko told the meeting that the measures are taken "in order to prevent the Russian Federation from forming private armies" on Ukrainian soil.

The announcement follows Thursday's decision by U.S. President Donald Trump to scrap the much-anticipated meeting with Russian leader Vladimir Putin. Trump said it isn't appropriate for him to meet with Putin since Russia hasn't released the Ukrainian seamen.

Meanwhile, the Ukrainian intelligence agency announced on Friday that they are investigating a senior cleric of the Russian Orthodox Church.

Ihor Guskov, chief of staff of the SBU intelligence agency, told reporters that its officers are searching the home of Father Pavlo, who leads the Pechersk Monastery in Kiev. He said the cleric is suspected of "inciting hatred."

The Pechersk Monastery, the spiritual center of Ukraine, is under the jurisdiction of the Russian Orthodox Church.

The Ukrainian church, which has been part of the Russian Orthodox Church for centuries, moved close to forming an independent church — fueled by the conflict with Russia Ukraine's Orthodox communities earlier this year.

There are currently three Orthodox communities in Ukraine, including two breakaway churches. Ukrainian authorities sought to portray the Russian Orthodox clerics in Ukraine as supporting separatists.

Ukraine's president announced on Thursday that the Constantinople patriarchy has approved a decree granting the Ukrainian Orthodox Church independence from the Russian Orthodox Church, a major boost to the president's approval ratings.

Both the Russian Orthodox Church and Russian authorities are strongly against the move and have warned Ukraine not to do it, fearing sectarian violence.

Russian government-appointed ombudswoman for Crimea told Russian news agencies that all the seamen have been transported from a detention center in Crimea. The three commanders have been taken to Moscow, she said. It wasn't immediately clear where the other 21 have been taken.

A Crimea court earlier this week ruled to keep the Ukrainian seamen behind bars for two months pending the investigation.

Ukraine's leader lobbied the nation's NATO allies on Thursday “to assist Ukraine and provide security” by deploying ships to the Sea of Azov, where the country is embroiled in a tense standoff with Russia.

President Petro Poroshenko, who implemented martial law across Ukraine’s border region for 30 days earlier this week, said Russia “wants nothing less but to occupy the sea [of Azov].”

“The only language he understands is the unity of the Western world,” Poroshenko said in an interview with the German daily Bild published Thursday. “Germany is one of our closest allies and we hope the states within NATO are now ready to relocate naval ships to the Sea of Azov in order to assist Ukraine and provide security."

Seized Ukrainian seamen speak on Russian TV

Seized Ukrainian seamen speak on Russian TV, and it is not clear if they are speaking under duress.

The tense stalemate between the two nations – ongoing since Russia’s annexation of the Crimean Peninsula in 2014 – escalated Sunday when the Russian coast guard reportedly fired on and seized three Ukrainian vessels and crews as the ships sought to pass from the Black Sea into the Sea of Azov through the Kerch Strait.

Ukraine has insisted its vessels were operating in line with international maritime rules, while Russia said they failed to get permission to pass.

“We have all the evidence on the table, everyone can see that it was Russian soldiers who attacked our Navy,” Poroshenko told Bild. “We had to react after this act of aggression and that’s why I have decreed martial law in some regions because we need to protect our country. It’s like 2014: Putin wants to annex another part of Ukraine, he behaves exactly as he did then.”

Meanwhile, Russia insisted the Ukrainian vessels were in its territorial waters and refused to communicate with the Russian coast guard or accept a Russian pilot to guide them through the narrow strait.

US calls for Russia, Ukraine to dial down tension

Secretary of State Pompeo calls on Russia to return vessels and crew to Ukraine; Rich Edson reports from the State Department.

"What were the border guards supposed to do?" Russian President Vladimir Putin said Wednesday. "They fulfilled their duty to protect the territorial integrity of the Russian Federation. If they had done something differently, they should have been put on trial for that."

There was no immediate reaction from German or NATO officials to Poroshenko’s request. While NATO condemned the Russian action, the allies will be unlikely to heed Poroshenko's request, which could trigger a confrontation with Russia. A 2003 treaty between Russia and Ukraine stipulates that agreement from each of the two littoral countries is required for warships from any other country to enter the internal sea.

PUTIN ACCUSES UKRAINIAN PRESIDENT OF PLAYING 'DIRTY GAME' AMID WARNINGS OF 'FULL-SCALE WAR' WITH RUSSIA

Putin, for his part, criticized the West for what he described as connivance with Ukraine's "provocation."

"The authorities in Kiev are successfully selling anti-Russian sentiments as they have nothing else left to sell," he said. "They can get away with whatever they do. If they want to eat babies for breakfast today, they will likely serve them too."

Poroshenko responded by ordering martial law in much of the country, a move that went into effect with parliamentary approval. Putin accused his Ukrainian counterpart of provoking the naval incident as a pretext to introduce martial law in a bid to shore up his sagging popularity and sideline competitors ahead of the March election.

The Associated Press contributed to this report.

Lucia I. Suarez Sang is a Reporter for FoxNews.com. Follow her on Twitter @luciasuarezsang

Russian President Vladimir Putin on Wednesday lashed out against Ukraine and accused the government of playing a “dirty game”, claiming they set up the naval incident that led to the seizure of three Ukrainian naval ships with the crew becoming prisoners.

Speaking during an investment forum in Moscow, Putin accused Ukrainian President Petro Poroshenko of attempting to score political points in a bid to get re-elected.

"This is a dirty game within the country [Ukraine],” Putin said. “It is a provocation initiated by the current authorities, and I think by the [Ukrainian] president, in light of the upcoming elections to be held next year."

— Vladimir Putin

“This is a dirty game within the country (Ukraine),” Putin said. “It is a provocation initiated by the current authorities, and I think by the (Ukrainian) president, in light of the upcoming elections to be held next year.”

“The incident in the Black Sea happened, it is a border incident, no more.”

Video

Putin’s remarks came after the Ukrainian government imposed the country’s first ever martial law in parts of the country that are vulnerable to a possible military action from Russia, with Poroshenko saying there was the “extremely serious” threat of a land invasion.

Western governments came out in support of Ukraine and accused Russia of violating international law. Earlier this week, NATO Secretary General Jens Stoltenberg told the Ukrainian president that the alliance is supporting the country’s “territorial integrity and sovereignty,” though Ukraine is not part of the military alliance.

TRUMP THREATENS TO CANCEL PUTIN MEETING AMID RUSSIA-UKRAINE TENSIONS

President Trump said he’s not “happy” about the situation and floated the possibility of canceling planned talks with Putin at this week's G20 summit in Buenos Aires. “I don't like that aggression,” Trump said in a recent interview with the Washington Post.

The Kremlin responded to the martial law in Ukraine with a pledge to deploy S-400 surface-to-air missile systems on the Crimean peninsula soon, according to the Interfax news agency.

Putin on Wednesday also reiterated the Kremlin’s story of how the clash between the ships occurred, saying Ukrainian vessels violated Russia’s territorial waters.

Russia’s main intelligence agency, the FSB, released a video on Tuesday that interviews three Ukrainian seamen, all of whom say Ukraine violated the Russian border. It was not immediately possible to ascertain if the men were talking under duress. One of them was apparently reading from a teleprompter.

But the video posted by Ukrainian Interior Minister Arsen Avakov appears to contradict Putin’s version of the event as it shows an apparent Russian commander shouting “slam him from the right” as the Russian vessel hits the Ukrainian ship.

Poroshenko on Tuesday appeared on national television and warned of the threat of “full-scale war” with Russia. “I don’t want anyone to think this is fun and games. Ukraine is under threat of full-scale war with Russia,” he said.

He went on to claim that Russia is building up its military presence along the Ukraine-Russian border, noting that with the number of tanks had tripled.

Ukraine and Russia have been involved in a long-term conflict starting in 2014. Russia-backed separatists have occupied parts of Eastern Ukraine and have held the control until this day, while Russia annexed Crimea in a referendum that most western countries deem illegal and illegitimate.

The Associated Press contributed to this report.

Lukas Mikelionis is a reporter for FoxNews.com. Follow him on Twitter @LukasMikelionis.

The tense tug-of-war between Russia and Ukraine escalated Monday, a day after three Ukrainian naval vessels were reportedly fired at and then captured by Russian coast guard ships – actions denounced by the U.S. ambassador to the United Nations as “outrageous” and a "provocation."

Nikki Haley, speaking at an emergency UN Security Council meeting Monday, said Russia’s reported actions in the Kerch Strait were an “outrageous violation of sovereign Ukrainian territory” and marked “yet another reckless Russian escalation.”

"[It's] an arrogant act that the international community must condemn," she added. "The United States will continue to stand with the people of Ukraine."

Haley’s comments come a day after a clash between the two contentious neighbors that began after the Ukrainian navy claimed a Russian coast guard vessel rammed a tugboat that was transporting artillery boats from Odessa on the Black Bea to Mariupol in the Sea of Azov, via the Kerch Strait.

Amb. Haley criticizes Russia for firing on Ukrainian ships

Addressing an emergency meeting of the U.N. Security Council, U.S. Amb. to the United Nations Nikki Haley says the U.S. stands with the people of Ukraine, calls on Russia to respect its international obligations.

The attack further escalated tensions between the two nations, which have been locked in a stalemate since Russia’s 2014 annexation of Crimea.

"We consider it as an act of aggression against our state and a very serious threat," Ukrainian President Petro Poroshenko said earlier Monday. "Unfortunately, there are no 'red lines' for the Russian Federation."

Poroshenko on Monday demanded Russia immediately release the sailors and ship seized, before signing a decree to introduce martial law across the country. Initially, he sought it for 60 days but later halved his proposal to 30 days in an apparent concession to opponents.

In a slew of Twitter posts, Poroshenko appeared to say that as “president and Supreme Commander” he has imposed martial law throughout the country, effective Wednesday.

“The introduction of martial law does not involve measures related to limiting the rights and freedoms of citizens or the introduction of censorship,” he said on Twitter.

The emergency measures, if approved, include a partial mobilization, a strengthening of the country’s air defense as well as a plethora of vaguely worded steps such as the “strengthening” of anti-terrorism measures and “information security.”

The clash Sunday began after the Ukrainian navy claimed a Russian coast guard vessel rammed a tugboat that was transporting artillery boats from Odessa on the Black Bea to Mariupol in the Sea of Azov, via the Kerch Strait.

“Russian coast guard vessels…carried out openly aggressive actions against Ukrainian navy ships,” the Ukrainian navy said in a statement, adding the tugboat’s engine, hull, side railing, and a lifeboat were damaged.

A ship under the Kerch bridge blocks the passage to the Kerch Strait near Kerch, Crimea. (AP)

The attack further escalated tensions between the two nations, which have been locked in a stalemate since Russia’s 2014 annexation of Crimea.

"We consider it as an act of aggression against our state and a very serious threat," the president said earlier Monday. "Unfortunately, there are no 'red lines' for the Russian Federation."

The two nations were quick to point fingers for Sunday’s clash with Ukraine maintaining its vessels were traveling in line with international maritime rules. Russia’s foreign minister claimed Ukraine violated international law and provoked the attack by sending its vessels through the Kerch Strait without permission.

“It’s obvious that this painstakingly thought-through and planned provocation was aimed at igniting another source of tension in the region in order to create a pretext to ramp up sanctions against Russia,” the Russian foreign ministry said in a statement.

“We’d like to warn the Ukrainian side that the policy of provoking a conflict with Russia in the area of the Sea of Azov and the Black Sea, which has been pursued by Kiev in coordination with the United States and the European Union, is fraught with serious consequences.”

The narrow strait is the only passage between the Black Sea and the Sea of Azov. It’s spanned by an 11.8-mile bridge that Russia completed this year.

"There is no doubt that it was done by blessing or, perhaps, even a direct order from the top," said Russian Foreign Minister Sergey Lavrov. "While planning that provocation, Ukraine had undoubtedly hoped to get additional benefits from the situation, expecting the U.S. and Europe to blindly take the provocateurs' side."

He urged the West to "calm down those in Ukraine who are trying to unleash a military hysteria to get political gains in connection with the planned elections" — a reference to Ukraine's presidential vote in March.

Ukrainian lawmakers listen to parliament speaker Andriy Parubiy, center, during a parliament session in Kiev, Ukraine, Monday, Nov. 26, 2018. Ukrainian President Petro Poroshenko has signed a bill to impose martial law in the country in the wake of Russia’s seizure of three ships and their crews. The Supreme Rada is due to vote on the issue later Monday for it to go into force. (AP Photo/Efrem Lukatsky)

The European Union and NATO called for restraint from both sides.

“We strongly support Ukraine sovereignty and territorial integrity within its internationally recognized borders, extending to its territorial waters,” Haley said. “We express our deep concern over the incident, which represent a dangerous escalation and violation of international law.”

NATO said Secretary-General Jens Stoltenberg expressed the U.S.-led military alliance’s “full support for Ukraine’s territorial integrity and sovereignty, including its full navigational rights in its territorial waters under international law.”

The incident came after months of incidents in the Sea of Azov that involved inspections and seizures of ships.

While a 2003 treaty designates the Kerch Strait and Sea of Azov as shared territorial waters, Russia has sought to assert greater control over the passage since the annexation of Crimea.

Fox News’ Bradford Betz and the Associated Press contributed to this report.

Lucia I. Suarez Sang is a Reporter for FoxNews.com. Follow her on Twitter @luciasuarezsang

A Kremlin-controlled television station released footage Tuesday purportedly showing three Ukrainian sailors confessing they were under orders to provoke the naval fracas with Russian warships off the coast of Crimea on Sunday.

The videos released by the FSB security service shows the three seamen — identified as Andriy Drach, Serhiy Tsybizov and Volodymyr Lisoviy — saying they were aware of the “provocative nature” of their actions. In one portion of the videos, which appear coached and were likely filmed under duress, one of the men appears to confirm that Ukraine violated the Russian border.

“We were warned by the Border Service of the Russian Federation that we were violating Russian law,” Drach, aboard the Nikopol gunboat, is shown saying to the camera. “They had repeatedly asked us to leave the territorial waters of the Russian Federation.”

Lesovoy, who identified himself as a divisional commander, reportedly said he “deliberately ignored requests via ultra-short-wave band” and that there were small arms on board as well as machine guns, the BBC reported.

Russia and Ukraine inch closer to war

President Trump says the United States is working with European partners to ease tension; Trey Yingst reports.

“I realized that the actions of the Ukrainian navy ships were of a provocative nature,” he said.

All the men appeared to be reciting memorized texts and one of them was clearly reading from a teleprompter.

Their statements come two days after Russian border guards fired at three Ukrainian navy vessels as they were trying to make their way through the Kerch Strait near Russian-occupied Crimea. The Russians seized the ships and their crews.

Ukraine demands release of sailors in Russian custody

Ukraine considering martial law after Russia seizes naval vessels; Trey Yingst reports on how both governments are responding to the conflict.

A court in the Crimean capital of Simferopol ordered Tuesday that one of the Ukrainian seamen be kept behind bars until Jan. 26.

The escalation over the weekend was the first overt military confrontation between Russia and Ukraine, who've been locked in a tense stalemate since Russia’s 2014 annexation of Crimea.

In response, the Ukrainian government Monday night imposed martial law for one month in parts of the country officials say are vulnerable to possible military action from Russia.

President Petro Poroshenko said the extraordinary measure was needed to strengthen the country’s defenses as there was the “extremely serious” threat of a land invasion from Russia.

“I have a document of intelligence in my hands…Here on several pages is a detailed description of all the forces of the enemy located at a distance of literally several dozen kilometers from our border. Ready at any moment for an immediate invasion of Ukraine,” he said, according to Reuters.

Meanwhile, the Kremlin warned Tuesday the declaration of martial law might trigger a flare-up of hostilities in eastern Ukraine.

The FSB claimed the ships had Ukrainian SBU intelligence agents onboard with a mission to mount what they called a "provocation" in the Kerch Strait.

The SBU on Tuesday confirmed the presence of its officers on the ships but denied any nefarious intentions, saying they were simply fulfilling counterintelligence operations for the Ukrainian navy.

Amb. Haley criticizes Russia for firing on Ukrainian ships

Addressing an emergency meeting of the U.N. Security Council, U.S. Amb. to the United Nations Nikki Haley says the U.S. stands with the people of Ukraine, calls on Russia to respect its international obligations.

The SBU also demanded Russia stop using "psychological and physical pressure" on the Ukrainians — an apparent reference to the interviews of the crewmembers that Russia released late Monday.

Russia and Ukraine have blamed each other for the confrontation that raised the specter of renewing a full-blown conflict in eastern Ukraine.

Ukraine said its vessels were heading to the Sea of Azov in line with international maritime rules, while Russia charged that they had failed to obtain permission to pass through the narrow Kerch Strait, which is spanned by a new bridge that Russia completed this year. The bridge is the only land border from the Russian mainland to the annexed peninsula of Crimea.

Russia was heavily criticized Monday at the United Nations by the U.S and other western nations for seizing the Ukrainian ships.

Meanwhile, German Foreign Minister Heiko Maas said Tuesday that Berlin has "called on Russia and Ukraine to show the greatest possible restraint" and suggested that Germany, France, Russia, and Ukraine could work together to resolve the tensions.

Fox News’ Lukas Mikelionis and the Associated Press contributed to this report.

Lucia I. Suarez Sang is a Reporter for FoxNews.com. Follow her on Twitter @luciasuarezsang

The tense tug-of-war between Russia and Ukraine escalated Monday, a day after three Ukrainian naval vessels were reportedly fired at and then captured by Russian coast guard ships – actions denounced by the U.S. ambassador to the United Nations as “outrageous” and a "provocation."

Nikki Haley, speaking at an emergency UN Security Council meeting Monday, said Russia’s reported actions in the Kerch Strait were an “outrageous violation of sovereign Ukrainian territory” and marked “yet another reckless Russian escalation.”

"[It's] an arrogant act that the international community must condemn," she added. "The United States will continue to stand with the people of Ukraine."

Haley’s comments come a day after a clash between the two contentious neighbors that began after the Ukrainian navy claimed a Russian coast guard vessel rammed a tugboat that was transporting artillery boats from Odessa on the Black Bea to Mariupol in the Sea of Azov, via the Kerch Strait.

Amb. Haley criticizes Russia for firing on Ukrainian ships

Addressing an emergency meeting of the U.N. Security Council, U.S. Amb. to the United Nations Nikki Haley says the U.S. stands with the people of Ukraine, calls on Russia to respect its international obligations.

The attack further escalated tensions between the two nations, which have been locked in a stalemate since Russia’s 2014 annexation of Crimea.

"We consider it as an act of aggression against our state and a very serious threat," Ukrainian President Petro Poroshenko said earlier Monday. "Unfortunately, there are no 'red lines' for the Russian Federation."

Poroshenko on Monday demanded Russia immediately release the sailors and ship seized, before signing a decree to introduce martial law across the country. Initially, he sought it for 60 days but later halved his proposal to 30 days in an apparent concession to opponents.

In a slew of Twitter posts, Poroshenko appeared to say that as “president and Supreme Commander” he has imposed martial law throughout the country, effective Wednesday.

“The introduction of martial law does not involve measures related to limiting the rights and freedoms of citizens or the introduction of censorship,” he said on Twitter.

The emergency measures, if approved, include a partial mobilization, a strengthening of the country’s air defense as well as a plethora of vaguely worded steps such as the “strengthening” of anti-terrorism measures and “information security.”

The clash Sunday began after the Ukrainian navy claimed a Russian coast guard vessel rammed a tugboat that was transporting artillery boats from Odessa on the Black Bea to Mariupol in the Sea of Azov, via the Kerch Strait.

“Russian coast guard vessels…carried out openly aggressive actions against Ukrainian navy ships,” the Ukrainian navy said in a statement, adding the tugboat’s engine, hull, side railing, and a lifeboat were damaged.

A ship under the Kerch bridge blocks the passage to the Kerch Strait near Kerch, Crimea. (AP)

The attack further escalated tensions between the two nations, which have been locked in a stalemate since Russia’s 2014 annexation of Crimea.

"We consider it as an act of aggression against our state and a very serious threat," the president said earlier Monday. "Unfortunately, there are no 'red lines' for the Russian Federation."

The two nations were quick to point fingers for Sunday’s clash with Ukraine maintaining its vessels were traveling in line with international maritime rules. Russia’s foreign minister claimed Ukraine violated international law and provoked the attack by sending its vessels through the Kerch Strait without permission.

“It’s obvious that this painstakingly thought-through and planned provocation was aimed at igniting another source of tension in the region in order to create a pretext to ramp up sanctions against Russia,” the Russian foreign ministry said in a statement.

“We’d like to warn the Ukrainian side that the policy of provoking a conflict with Russia in the area of the Sea of Azov and the Black Sea, which has been pursued by Kiev in coordination with the United States and the European Union, is fraught with serious consequences.”

The narrow strait is the only passage between the Black Sea and the Sea of Azov. It’s spanned by an 11.8-mile bridge that Russia completed this year.

"There is no doubt that it was done by blessing or, perhaps, even a direct order from the top," said Russian Foreign Minister Sergey Lavrov. "While planning that provocation, Ukraine had undoubtedly hoped to get additional benefits from the situation, expecting the U.S. and Europe to blindly take the provocateurs' side."

He urged the West to "calm down those in Ukraine who are trying to unleash a military hysteria to get political gains in connection with the planned elections" — a reference to Ukraine's presidential vote in March.

Ukrainian lawmakers listen to parliament speaker Andriy Parubiy, center, during a parliament session in Kiev, Ukraine, Monday, Nov. 26, 2018. Ukrainian President Petro Poroshenko has signed a bill to impose martial law in the country in the wake of Russia’s seizure of three ships and their crews. The Supreme Rada is due to vote on the issue later Monday for it to go into force. (AP Photo/Efrem Lukatsky)

The European Union and NATO called for restraint from both sides.

“We strongly support Ukraine sovereignty and territorial integrity within its internationally recognized borders, extending to its territorial waters,” Haley said. “We express our deep concern over the incident, which represent a dangerous escalation and violation of international law.”

NATO said Secretary-General Jens Stoltenberg expressed the U.S.-led military alliance’s “full support for Ukraine’s territorial integrity and sovereignty, including its full navigational rights in its territorial waters under international law.”

The incident came after months of incidents in the Sea of Azov that involved inspections and seizures of ships.

While a 2003 treaty designates the Kerch Strait and Sea of Azov as shared territorial waters, Russia has sought to assert greater control over the passage since the annexation of Crimea.

Fox News’ Bradford Betz and the Associated Press contributed to this report.

Lucia I. Suarez Sang is a Reporter for FoxNews.com. Follow her on Twitter @luciasuarezsang

A Kremlin-controlled television station released footage Tuesday purportedly showing three Ukrainian sailors confessing they were under orders to provoke the naval fracas with Russian warships off the coast of Crimea on Sunday.

The videos released by the FSB security service shows the three seamen — identified as Andriy Drach, Serhiy Tsybizov and Volodymyr Lisoviy — saying they were aware of the “provocative nature” of their actions. In one portion of the videos, which appear coached and were likely filmed under duress, one of the men appears to confirm that Ukraine violated the Russian border.

“We were warned by the Border Service of the Russian Federation that we were violating Russian law,” Drach, aboard the Nikopol gunboat, is shown saying to the camera. “They had repeatedly asked us to leave the territorial waters of the Russian Federation.”

Lesovoy, who identified himself as a divisional commander, reportedly said he “deliberately ignored requests via ultra-short-wave band” and that there were small arms on board as well as machine guns, the BBC reported.

Russia and Ukraine inch closer to war

President Trump says the United States is working with European partners to ease tension; Trey Yingst reports.

“I realized that the actions of the Ukrainian navy ships were of a provocative nature,” he said.

All the men appeared to be reciting memorized texts and one of them was clearly reading from a teleprompter.

Their statements come two days after Russian border guards fired at three Ukrainian navy vessels as they were trying to make their way through the Kerch Strait near Russian-occupied Crimea. The Russians seized the ships and their crews.

Ukraine demands release of sailors in Russian custody

Ukraine considering martial law after Russia seizes naval vessels; Trey Yingst reports on how both governments are responding to the conflict.

A court in the Crimean capital of Simferopol ordered Tuesday that one of the Ukrainian seamen be kept behind bars until Jan. 26.

The escalation over the weekend was the first overt military confrontation between Russia and Ukraine, who've been locked in a tense stalemate since Russia’s 2014 annexation of Crimea.

In response, the Ukrainian government Monday night imposed martial law for one month in parts of the country officials say are vulnerable to possible military action from Russia.

President Petro Poroshenko said the extraordinary measure was needed to strengthen the country’s defenses as there was the “extremely serious” threat of a land invasion from Russia.

“I have a document of intelligence in my hands…Here on several pages is a detailed description of all the forces of the enemy located at a distance of literally several dozen kilometers from our border. Ready at any moment for an immediate invasion of Ukraine,” he said, according to Reuters.

Meanwhile, the Kremlin warned Tuesday the declaration of martial law might trigger a flare-up of hostilities in eastern Ukraine.

The FSB claimed the ships had Ukrainian SBU intelligence agents onboard with a mission to mount what they called a "provocation" in the Kerch Strait.

The SBU on Tuesday confirmed the presence of its officers on the ships but denied any nefarious intentions, saying they were simply fulfilling counterintelligence operations for the Ukrainian navy.

Amb. Haley criticizes Russia for firing on Ukrainian ships

Addressing an emergency meeting of the U.N. Security Council, U.S. Amb. to the United Nations Nikki Haley says the U.S. stands with the people of Ukraine, calls on Russia to respect its international obligations.

The SBU also demanded Russia stop using "psychological and physical pressure" on the Ukrainians — an apparent reference to the interviews of the crewmembers that Russia released late Monday.

Russia and Ukraine have blamed each other for the confrontation that raised the specter of renewing a full-blown conflict in eastern Ukraine.

Ukraine said its vessels were heading to the Sea of Azov in line with international maritime rules, while Russia charged that they had failed to obtain permission to pass through the narrow Kerch Strait, which is spanned by a new bridge that Russia completed this year. The bridge is the only land border from the Russian mainland to the annexed peninsula of Crimea.

Russia was heavily criticized Monday at the United Nations by the U.S and other western nations for seizing the Ukrainian ships.

Meanwhile, German Foreign Minister Heiko Maas said Tuesday that Berlin has "called on Russia and Ukraine to show the greatest possible restraint" and suggested that Germany, France, Russia, and Ukraine could work together to resolve the tensions.

Fox News’ Lukas Mikelionis and the Associated Press contributed to this report.

Lucia I. Suarez Sang is a Reporter for FoxNews.com. Follow her on Twitter @luciasuarezsang

Ukraine's parliament voted on Monday to impose martial law for 30 days, one day after tensions rose as Russia allegedly fired at three Ukrainian naval vessels near Russia-occupied Crimea.

The Ukrainian ships, along with their crews, were seized by Russian coast guard ships.

Ukraine's navy said six sailors were wounded after Russian coast guards opened fire on the three Ukrainian ships near the Kerch Strait — the only outlet for Ukrainian vessels to the Black Sea — and then seized them. Ukraine is demanding the release of the ships and crewmen.

Martial law in the country is set to include a partial mobilization and strengthening of the country's air defense. The measures before parliament also included vaguely worded steps such as "strengthening" anti-terrorism measures and "information security."

UN calls emergency meeting after Russia seizes Ukraine ships

Speaking at an emergency meeting of the United Nations Security Council on Monday, U.S. Ambassador to the U.N. Nikki Haley called Russia's reported actions an “outrageous violation of sovereign Ukrainian territory,” saying they marked “yet another reckless Russian escalation.”

"[It's] an arrogant act that the international community must condemn," she added. "The United States will continue to stand with the people of Ukraine."

Russian Foreign Minister Sergey Lavrov, however, said Ukraine violated international law and provoked Russia by sending its navy vessels through the Kerch Strait without permission — a claim Ukraine's Ambassador to the U.N. Volodymyr Yelchenko called an "outright lie."

Ukraine and Russia have been locked in a stalemate since Moscow annexed Crimea in 2014.

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NATO said Secretary-General Jens Stoltenberg expressed the U.S.-led military alliance’s “full support for Ukraine’s territorial integrity and sovereignty, including its full navigational rights in its territorial waters under international law.”

The incident came after months of incidents in the Sea of Azov that involved inspections and seizures of ships. While a 2003 treaty designates the Kerch Strait and Sea of Azov as shared territorial waters, Russia has sought to assert greater control over the passage since the annexation of Crimea.

Fox News’ Lucia Suarez Sang and The Associated Press contributed to this report.